Process for the production of highindene-content hydrocarbon oils



April 14, 1942. K. H. ENGEL 2,279,780

PROCESS FOR THE PRODUCTION OF HIGH- INDENE"CO NTENT HYDROCARBON OILS Filed May 15, 1940 LOW-INDENE LOW-INDENE on. SEPARAT'W OIL OF +AGENT 1 AGENT INDENE AGENT FRACTION AZEOTROPIC FRACTION- 4 AGENT ATON 'NDENE CHILLING If DISTILLATE STEP DISTILLATION HIGH'INDENE FILTR ATION LOW-INDENE 1 HIGH-BOILING souo RESIDUE INDENE INVENTOR KARL H. ENGEL BY 6 Z ATTORNEY Patented Apr. 14, 1942 raocnss ron THE PRODUCTION or men- INDENE-CONTENT HYDROCARBON on.s

Karl E. Engel, West Englewood, N. J., assignor, by mesne assignments, to Allied Chemical & Dye Corporation, a corporation-of New York Application May 15, 1940, Serial No. 335,331

Claims.

This invention relates to the production and purification of indene-containing oils and more particularly to the production of hydrocarbon oils of a high indene content from hydrocarbon oils of relatively low indene content.

Indene has heretofore been recovered from crude indene-containing hydrocarbon oils by treating them with substances such as sodium amide or potassium hydroxide whereby the alkali metal compound combines with the indene to produce a compound which separates from the hydrocarbon oils. The indene is then recovered from the compound thus formed by hydrolysis. Indene has also been recovered from indenecontaining hydrocarbon oils by fractionating the oils to obtain a fraction having an indene content of about 80% and then cooling the fraction to temperatures of about -25 C. to cause the indene to freeze and separate from the oils. Fractionation of indene-containing hydrocarbon oils by the usual distillation methods, no matter how carefully conducted, fails to produce oils of an indene content substantially higher than 8081% for the reason that many of the oils contained in crude indene-containing hydrocarbon oils have practically the same boiling point as indene and therefore cannot be separated therefrom by ordinary fractionation. None of theabove methods of obtaining indene have been found to be commercially satisfactory from an methylbenzenes and 'other alkylated benzenes and also paraflinic hydrocarbons, which have in the mixtures in question substantially the same distillation temperatures asindene and which therefore cannot be separated from indene by ordinary fractional distillation. As a result of extensive development work in this field I have made the surprising discovery that indene may be separated from such non-indene oils by distilling the indene-containing hydrocarbon oil in the presence of an agent capable of forming azeotropes with indene and the non-indene oils contained in the hydrocarbon oil; I have found that indene and the non-indene oils form azeotropes of the minimum-boiling type; i. e., the

azeotropes distill at temperatures lower than the distillation temperatures of any of the azeotrope consituents, and that the indene azeotropes and the indene have substantially higher distillation temperatures than the distillation temperatures of the non-indene azeotropes; thus separation by distillation of the indene and the indene azeotropes from the non-indene azeotropes may be effected. This discovery is indeed surprising because the close chemical relationship existing between the constituents of the indene-containing hydrocarbon oil and the fact that indene and the non-indene oils have subsantially the same distillation temperatures would not lead a chemist to expect that the addition of a single agent to the complex mixture of hydrocarbons would effeet the formation of azeotropes such that on distillation substantially all of the non-indene azeotropes distill 0115, leaving an oil of high indene content in the still. As contrasted with the indene content of oils produced by ordinary fractionation, the process of this invention makes possible the production of substantially pure indene---upv to 98% or more-by a fractional distillation process. and claims the term agent is intended to refer to those substances added to the hydrocarbon oil of relatively low indene content to form azeotropes with indene and the non-indene oils contained therein.

y In the course of my development work, I have observed that certain organic compounds are particularly suitable for use as agents in the recovery of indene from crude indene-containing hydrocarbon oils by the process of my invention.

I have found that these compounds possess the containing oils to polymerize on distillation to any undesirable degree.

(4) They contain a radical which renders the compounds relatively strongly polar as compared with indene and other substances present in crude indene-containing hydrocarbon oils and which makes the compounds soluble in water or in aqueous solutions of acids or bases. .Among such radicals may be mentioned 0H, COOH, NH-: and the. aromatic heterocyclic nitrogen radical containing pyrldinic nitrogen such as is found in pyridine, quinoline, etc.

(5) They are separable from the non-indene oils distilled from the crude indene-containing Throughout the specification or an aqueous solution of an acid or base.

In the following table several compounds are listed having the above characteristics and which I have found to be extremely suitable for use as agents in the practice of my invention:

Polar Boiling Compound ,gmup Soluble in point oc Phenol"--. -0H- H,0,aq.alkali 183 Ethylenegi col 0H 4, H, 197 Propylenegycol 0H 11,0 187.4 Diethzlene glycol mono- OH. H 0 193.2

met yl ether. o-chlorfihenol OH Aq. alkali 174-175 oCreso 0H Aq.allrali 191 Butyrlc acid -CO0H,. H 0 163.5 Aniline NH,. Aq.acid. 184.4 Monoethanol amine {:g }H,0 172 Pyridine base fractions Pyridlnic Aq. acid 17i-l81 from tar. nitrogen.

Indene-containing hydrocarbon oils, as.is well known. may be obtained by fractional distill'ation of coal tar oils, drip oils, carburetted watergas tar oils, oil-gas-tar oils, andlight oils recovered in coal gas and water-gas operations. In accordance with this invention, the indene-containing oils are mixed with an agent which will form azeotropes with the constituents of the oils and the mixture is then fractionally distilled to effect the separation of the non-indene azeotropes from the indene and the indene azeotrope, Distillation may be carried out under a partial vacuum if desired, thus' permitting greater heat economy without affecting the efficiency of the separation of indene and non-indene oils. It should be noted, however, the ratio of hydrocarbon oil to agent in the azeotrope may change slightly at reduced pressures, generally increasing. Since the agents used in accordance with this invention form minimum-boiling azeotropic mixtures, it has been found desirable, before the addition of the agent, to subject the indene-containing oils to be treated according to the invention to ordinary fractional distillation in order to remove non-indene oils of a substantially different boilin range from indene, particularly those of substantially higher boiling range than indene.

tropic ratio of agent to non-indene oils in the distillate will be maintained throughout the fractionation. The entire amount of agent'may be added to the indene-containing hydrocarbon oil before fractionation: or the agent may be added gradually in a continuous or intermittent fashion during the course of the fractionation.

Atthe beginning of the fractionation the distillate consists almost entirely of the azeotropic mixture of the non-indene oils and agent, but as fractionation proceeds and the temperature approaches the distillation temperature of the The removal of these oils reduces the amount of agent required for the distillation,

indene azeotrope, the indene content of the distillate increases. The course of the fractionation may be followed by taking samples of the distillate and testing them for their indene content. The point atwhich fractionation is discontinued depends upon the indene content of the hydrocarbon oil being treated, the desired indene content of the final product and the efllciency of the agent used in separating the indene and nonindene oils.. Thus the lower the indene content of the hydrocarbon oil being treated and the higher the desired indene content of the final product, the longer fractionation of the oil must be continued; while the higher the separation efliciency of the agent, the shorter will be the time necessary to obtain a hydrocarbon oil of the desired indene content. Obviously the longer fractionation is continued, the smaller will be the yield of the desired high-indene-content hydrocarbon oil. If desired, fractionation may be continued until substantially the entire indene content charge has been distilled, thereby recovering from the last distillate cut an oil containing about 98% indene. Fractionation of the'mixture, however, is ordinarily discontinued when the indene content of the distillate shows the still residue contains about 89% to 95% indene (exclusive .1 may be then recycled through the above-described process to recover the indene contained therein, agent being added as necessary: or it may be treated in the ordinary manner with sulfuric acid to polymerize the indene and obtain hydrocarbon oils for solvent purposes and the like.

The accompanying drawing is a flow diagram illustratinga preferred method of carrying out the. process of my invention.

Reference numeral I indicates an azeotropic fractional distillation operation in which a mixture of azeotropic agent and a close-cut indene fraction, e. g. a drip oil high-flash naphtha fraction of boiling range 176-183' 0., enter the process as indicated at 2 and are subjected to azeotropic distillation. As above indicated, the overhead product consists primarily of an azeotrope of the agent and non-indene components of the oil. This mixture is treated as indicated at 3 to separate the agent from the oil. As above indicated, inthe case of a number of'agents, such as glycol compounds, the separation may be brought about merely by cooling the mixture to room temperature and decanting; the separated agent may thenbe returned to the azeotropic fractionation step as indicated at 4. The low indene oil from which the agent has been separated is withdrawn as indicated at 5. As above stated, fractions of this oil may contain appre- 1 ciable quantities of indene and may therefore be recirculated in the process or treated by other means to recover indene contained therein.

The high indene oil withdrawn as residue from the azeotropic fractionation may contain traces of azeotropic agent which may be removed as above indicated. The high indene oil is then subjected to distillation as indicated at 6 to produce an indene distillation which may contain up to about 98% indene. The high-boiling residue which contains some indene may be treated to recover the indene contained therein. The indene distillate may be further subjected to a chilling operation indicated at I as hereinafter described, and the solid indene thus formed may be separated by filtration as indicated at 8. The filtrate fromthis operation may be reworked to recover indene contained therein.

The following examples are illustrative of the practice of this invention. Amounts are given in parts by volume. The indene percentages were calculated from the relation of the specific gravity of the oil to that of a similar oil of known indene content. v

Example 1.-500 parts of drip oil high-flash naphtha of a boiling range from 176 to 183 C., a specific gravity at 22 C. of 0.957 and an indene content of 78% were mixed with 125 parts of phenol. This mixture was then fractionated in a 32-ball 7-foot column. Distillate cuts of 50 parts each were tested to determine their specific gravity, the phenol was then removed by washing with alkali, the ratio of distillate oil to phenol calculated, and the specific gravity of the phenolfree distillate oil determined. From the specific gravity of the phenol-free oil, its indene content was calculated. The following table shows theresults of these tests:

"Sp. gr. of Sp. gr. of

Column distillate Bat, phenol-[rec of dlso distillate dist|l1ate Hate tunp. out at 22 G. ow hem] distillate on 4 (inc. phenol) P oil at 22 C. Percent 174. 5 (No determinations made of these fractions 175. 5 because of small size of fractions) Fracti0nation was discontinued after 325 parts of distillate had been recovered and the still residue was then distilled straight, yielding, after removal of the small amount of phenol contained therein, 270 parts of an oil ofspecific gravity of 0.983 at 22 C. and an indene content of 94%. By this method for every 100 parts of crude highfiash naphtha, approximately 44 parts of an oil containing 55% indene and 54 parts of an oil containing 94% indene were obtained.

When the same oil was fractionated in the same column at the same rate without the use of phenol, it was impossible to obtain an oil of higher indene content than about 81% thereby.

Example 2.-500 parts of a crude carbolic oil high-flash naphtha cut boiling from 178 to 183 0., having aspecific gravity of 0.951 at 22 C. and an indene content of 68%, were mixed with 125 parts of phenol, the mixture was fractionated as in Example 1, with the following re- Sp. gr. o1 Sp. gr. of Par-ts Column distillate .Rgm phenol-free of disa distillate distlllato m1 me temp. out at 22 0. hem). distillate on (me. phenol) oil at 22" 0.

C'. Percent 0 1M l0 167 20 168 30 168. 5 50 188. 5 0. 945 68/32 0. 894 23 Fractionation was discontinued after 400 parts'of distillate had been recovered. The still residue was then distilled straight, yielding, after removal of the small amount of phenol contained therein, 220 parts of an oil,of specific gravity at 22 C. of 0.980, and having an indene content of 91%.

Example 3.-500 parts of crude carbolic oil high-flash naphtha, boiling from 181 to 183 0., having a specific gravity of 0.958 at 22 C. and an indene content of 74% were mixed with 150 parts of phenol and the mixture was fractionated in a, packed column at a pressure of about 280 mm. mercury. Distillate cuts were tested by washing the cuts with alkali to remove the phenol, calculating the ratio of distillate .oil to phenol, and then determining the specific gravity of the distillate oil. From the specific'gravity of the phenol-free oil, its indene content was calculated. The following table shows the results of these tests:

lndcnc distillate oil Ratio distillate 0i1/ phenol Percent Fractionation was discontinued alter 255-parts of distillate had been recovered and the still residue was then distilled straight, yielding, after removal of the remaining phenol contained therein, 305 parts of an oil of specific gravity of 0.983 at 22 C., and an indene content of 92%. Thus for every'l00 parts oi crude high-flash naphtha containing 74% indene, approximately 37 parts of an oil containing 52% indene and about 61 parts of an oil containing 92% indene were obtained.

Example 4.500 parts of a drip oil high-flash naphtha fraction boiling from 176 to 183 C., having a specific gravity or 0.948 at 22 C. and

an indene content of 70% were mixed with 110 parts of ethylene glycol, and the mixture was fractionally distilled in a 32-ball 7-ioot column.

The glycol separated from the distillate oil when cooled to 22 C. Distillate cuts of 70 parts each were tested by permitting the glycol to separate from the distillate oil, washing the oil with water to remove traces of glycol, drying, and then determining the specific gravity of the oil. The small amounts of hydrocarbon oils remaining in the glycol were-separated by dilution with water and the glycol reused. The following table shows the results of these tests:

Sp. gr. glycol-free distillate oil at 22 Indene distillato oil Ratio distillate Percent 70 30' 0. lies Fractional distillation was discontinued after 420 parts oi distillate had been recovered and the still residue was then distilled straisht, yielding, after separation of the glycol contained therein, 187 parts oi an oil of specific gravity at 22 C. of 0.977 and an indene content 0! 91.5%.

Example 5.-500 parts of a drip oil high-flash naphtha fraction boiling from 176 to 183' 0., with a speciiic gravity oi 0.948 at 22 C. and an indene content of 70%,, were mixed with 110 parts of propylene glycol, and the mixture was then fractionally distilled in a 32-ball 7-1oot column. The glycol separated from the distillate oil when cooled to 22 C. Distillate cuts, of 70 parts each were tested by permitting the glycol.

to separate from the distillate oil, washing the oil with water to remove traces of glycol, drythe oil. The following table shows the results of these tests:

R a 5i" ilt: a 0 c0 Parts of distillate fi' distillate distillate 25m? oil/glycol oil 16: 22 0 Percent Fractionation was discontinued after 420 parts of distillate had been recovered and the still residuewas then distilled straight, yielding, after separation of the small amount of glycol contained therein, 180 parts of an oil or specific gravity at 22 C. of 0.982 and containing indene. By combining the last out, i. e the cut from 350-420 parts, with the straight distillate and separating glycol therefrom, 225 parts of a hydrocarbon oil containing 93.5% indene were obtained.

Example 62-500 parts 01 a drip oil high-flash naphtha fraction boiling from 176 to 183 0., having a specific gravity of 0.948 at 22 C. and an indene content of 70% were mixed with parts of diethylene glycol mono-methyl ether and the mixture was then iractionally distilled in a 32-ball 7-ioot column. The glycol ether separated irom the hydrocarbon oil in the distillate when cooled to 22 C. Distillate cuts of 70 parts each were tested by permitting the glycol ether to separate 'irom the hydrocarbon oil. washing Sp. gr. oi Ratio glycoletherindene Parts oidistiilate heedhmania mum ii her 0 oil nt22C.

Percent ao/m 0.0m 44 1726 nm em 51 an indene content of 68%, were mixed with 175 then determining thespecific gravity of the disfig gg g S1l .gr. oi 45 tillate oil,,with the following results: Parts lumn out (in- Ratio dis- 2 23 Indene oidiseluding tillate 011 distillate distillate tillate o-chlorchlorphenol oil 2 SID-8 f Pheml) at 21 Parts of distillate Cdum l l tz aniline'm d l l t 22 0. temp. g distillate oil e at 22 0. 0. Percent 50 16 6 C. Percent 174.3 1.072 44 50 0.000 11 108 174. 4 1. 091 /54 0. s90 10 171 175. 5 1. 092 40 54 0. 922 172. 5 175. 7 1. 092 40 54 0. 927 49 173.5 00 4 0. s27 33 An additional parts of o-chlorphenol were charged to the still at this point, and fractionation continued. 5

- 174' 5 00 34 0. 91s 53 An additional 125 parts of o-clllorphenol were charged to the still I at this point, and fractionation continued. 8

200 175 00 a4 0. 935 03 350 175.0 1.120 34 00 0.914 as I 415 175.1 1.128 34 00 0.984 54 220 175 Fractionation was discontinued after 415 Parts 270 I of distillate had been recovered. The still resi- 170 00 04 0. 95s 79 due was then washed with alkali to remove residm ual chlorphenol and distilled straight, yielding 170 4 n 198 parts of an oil of specific gravity of 0.980 at 77 7 m an indene content of 68%, were mixed with 350 Pl dRaliio s r. r parts of o-chlorphenol and the mixture frac- 8 111119118 tionated in a 32-ball 7-foot column Distillate Parts Oldistillate tem oil/glycol roe disdistillate p mm 01 181 01] cuts of 100 parts each were tested to determlne 5 their specific gravity, the chlorphenol was then a removed by washing with alkali, the ratio of dis- 5 tillate oil to chlorphenol calculated, and the spe 17a cific gravity of the chlorphenol-free distillate 173 '9/21 59 oil determined. The following table shows 1 the 171 10 results of these tests: 17 174 /21 0.940 08 Sp. gr. oi 1 1 distillate ,3- f' lgairts Column ci1td( inftfitiigdis- 'i g g' Indene 0 1scu in i T 111. 175 79 21 0.052 15 011.110 M11105 clllo zph ni ll 2 01 1 175 P116208 at a "5 22 176 176 82/18 0- 31 0'. Percent 5 171.2 1 173.9 1 090 30/02 0 809 a Fractlonation was discontinued after 420 parts 20 3 324% 85% of distillate had been recovered and the still resi- 1 51 11133 3 '9 '2 due was then distilled straight, yielding, after Separation of the small amount of glycol ether All additional 150 parts of ochlorpllenol were added to the stil 1 contained therein 15 a t of a hydrocarbon charge at this point, and fractionation continued. oil having a specific gravity of 0.980 at 22 C. 25

and containing 92% 1 500 175.7 1.152 30/70 0.945 63 000 175.7 1.153 3208 0.9 Example 7.500 parts of a carbollc oll lngh- 0 17 1.140 40400 0.923 {if flash naphtha cut boiling from 178 to 183 C.,

havmg specific gravity of at 22 and 30 Fractionation was. discontinued after 700 parts of t distillate had been recovered. The still residue parts o'cmorphenol and the nuxture was then was then washed with alkali to remove residual termine their specific gravity, the chlorphenol m an speclzic g at 22 of was then removed by washing with alkali, the 35 jf 2 56 f; 2 f 3 hi h fi h ratio of distillate oil to chlorphenol calculated, n f g3. f 2 t g and the specific gravity of the chlorphenol-iree 111.11g mm distillate oil determined. An additional 50 and Speclfi" 1957 i 22 and parts of o-chlorphenol were charged into the an indene content of 78% i mlxed i 125 still after 200 and 300 parts of distillate respec i l and the mlxture fraciwlmuy tively had been conectei The following table distilled in a 32-ball T -foot column. Dlstlllate Shows the results of these tests, 7 cuts were tested by washing with dilute hydrochloric acid and water to remove the aniline, and

22 C. and an indene content of 90%.

.Example 8.500 parts of a carbolic all high-' Fractionation was discontinued after 370 parts of flash naphtha cut boiling from 178 to 183 C.. distillate had been recovered and the still residue having a specific gravity of 0.951 at 22 C. and 7 was then distilled straight, yielding, after removal of the small amount of aniline contained therein, 195 parts of a hydrocarbon oil of specific gravity 0.981 at 22 C. and containing 92.5% indene.

Example 10.500 parts of a carbolic oil highfiash naphtha cut boiling from 178 to 183 C., having a specific gravity of 0.951at 22 C. and an indene content of 68%, were mixed with 200 parts of a tar base fraction boiling from 170 to l86.5 C. and containing pyridine bases and about 48% aniline, and the mixture was then fractionally distilled in a 32-ba11 'l-toot column. Distillate cuts of 100 parts each were tested to determine their specific gravity, tar bases were then removed by washing with hydrochloric acid, the ratio of distillate oil to tar base fraction calculatedyand the specific gravity of the tar basefree oil determined. The following table shows the results of these tests:

3mg?! Bp. gr. of

to tar base tillate hm oil/tar base on oil C. Percent 150.0 170.8 0.983 65/35 0.904 25 177.5 0.946 66/36 0.018 41 178.4 0.055 55/35 0.935 55 170.0 0.000 70/30 0.050 75 l80.8 0077 78/22 0.073 84 Fractionation was discontinued after 500 parts of distillate had been recovered. The still residuewas washed with hydrochloric acid to remove residual tar bases and distilled straight, yielding 121 parts of an oil of specific gravity of 0.986 at 22 C. and an indene content of 95%.

Example 11.-500 parts of a drip oil high-flash naphtha fraction, boiling from 176 to 183 0.,

8p. gr. of ethanolamins'free distillate oil at22 0.

Ratio distillate oil/ethanolamine indene distillate oil Percent (Not determined) 0. 908

Fractionation was discontinued after 350 parts of distillate had been recovered, and. the still residue was then distilled straight, yielding, after separation of the small amount of amine contained therein, 185 parts of an oil of specific gravity of 0.980 at 22 C. and containing 92% indene.

Certain of the agents used in accordance with this invention, while miscible with the indenecontaining hydrocarbon oils at distillation temperatures so that azeotropes are formed by these agents with indene and the non-indene oils, are immiscible with the hydrocarbon oils at room temperatures so that they separate therefrom at room temperatures. As examples of agents of this type may be mentioned ethylene glycol, proylene glycol, diethylene glycol mono-methyl ether and mono-ethanol amine. The property of immiscibility of these agents with hydrocarbon oils at room temperatures (about 22 C.) is particularly advantageous, for it permits separation of the agent from the hydrocarbon oils to be efiected by mere decantation. The agent thus decanted may be reused in the fractionation of the indene-containing hydrocarbon oil, thus permitting the proper azeotropic ratio of agent to hydrocarbon oil to be maintained in the fractionating column with the use of a minimum amount of agent, obviating the necessity of keeping in storage large quantities of agent for carrying out the fractionation. The following example illustrates this phase of my invention:

Example 12.-16,450 parts of drip oil highflash naphtha boiling'from 176 to 183 C., having a specific gravity of 0.937 at 155 C. and an indene content of 54% were mixed with 1,000 parts of propylene glycol and the mixture fractionated in a packed column. The distillate was condensedand permitted to separate into two layers, the lower propylene glycol layer being continuously withdrawn and returned to the bottom of the iractionating column for reuse. The hydrocarbon oil layers separated in the condenser were tested periodically, after removal of the small amounts of propylene glycol remaining in the oils, to determine their specific gravity, from which their indene contents were calculated. The

tested gives the results of these tests:

Sp. gr. of Parts of Volume propylene Indene in pro ylene Cut No. of cut glycol-tree distillate yool tested distillate oil removed at 155 C I with oils Percent l, I!) 0.905 29 4 1, 370 7 0.012 34 4 1, 000 0. 02a 47 e l, 0.933 51 7 560 0.947 62 5 but was slightly contaminated with hydrocarbon oils. It can be reused for further separation of indene and non-indene oils. Thus, for every 100 parts of crude high-flash naphtha containing 54% indene, the distillation yielded about 67 parts of an oil containing 34% indene and about 21 parts of an oil containing 90% indene.

If it is desired to obtain pure indene from the hydrocarbon oils of high indene content obtained according to the practice of this invention, the hydrocarbon oils may be cooled to from about to about C. and the solid indene thus formed may be separated from the oils.

From the above description it will be evident this invention provides a simple and inexpensive method of obtaining oils of a high indene content from oils of a relatively lowindene content;

My copending applications Serial Nos. 335,329 and 335,330, filed on the same date as the present application, are directed to species of the generic invention disclosed and claimed in this application.

In the claims the term "tar base is intended to include not only tar base fractions recovered from coal tar, which fractions may contain pyridine bases, or aniline, or both, but it is also intended toinclude substantially pure tar bases,

which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an organic compound having a radical selected from the group consisting of the hydroxyl, the carboxyl, the amino, and the pyridinic nitrogen radicals and capable of forming azeotropes with indene and the non-indene oils contained in the hydrocarbon oil. I

2. In a method of producing a hydrocarbon oil of high indene content from a hydrocarbon oil of relatively low indene content, the step which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an organic compound containing a hydroxyl group and capable of forming azeotropes with indene and the non-indene oils contained in the hydrocarbon oil.

of relatively low indene content in the presence of an organic compound containing a pyridinic nitrogen radical and capable of forming azeotropes with indene and the non-indene oils contained in the hydrocarbon oil.

4. In a method of producing a hydrocarbon oil of high indene content from a hydrocarbon oil of relatively low indene content, the step which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an organic compound containing an amino group and capable of forming azeotropes with indene and the non-indene oils contained in the hydrocarbon oil.

5. In a method of producing a hydrocarbon oil of high indene content from a hydrocarbon oil of relatively low indene content, the step which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an amount of tar base sumcient to form an azeotrope with non-indene components of the oil.

6. In a method "of producing a hydrocarbon oil of high indene content fromv a hydrocarbon oil of relatively low indene content, the step to form an azeotrope with non-indene components of the oil. 7. In a method of producing a hydrocarbon oil of high indene content from a hydrocarbon oil of relatively low indene content, the step which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an amount of o-chlorphenol sumcient to form an.

azeotrope with non-indene components of the oil.

8-. In a method of producing a hydrocarbon oil of high indene content from a hydrocarbon oil of relatively low indene content, the step which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an organic compound having a radical which renders the compound relatively strongly polar as compared with indene and other substances present in the hydrocarbon oil and which makes the compound soluble in water or in aqueous solutions of acids or bases, said compound being miscible with the hydrocarbon oil at distillation temperatures, separable therefrom by gravity or on aqueous extraction, chemically inert with respect to the constituents of the hydrocarbon oil, capable of forming azeotropes with indene and the non-indene oils contained therein, and having a distillation temperature at atmospheric pressure of between about 145 and about 220 C.

'9. In a method of producing a hydrocarbon oil of high indene content from a hydrocarbon oil of relatively low indene content, the step .which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an amount of aniline sumcient to form an azeotrope with non-indene components of the oil.

10. A method of producing pure indene from a hydrocarbon oil of relatively low indene content having a boiling range in the neighborhood of indene boiling point, which comprises distilling the hydrocarbon oil of relatively low indene content in the presence of an organic compound having a radical which renders the compound relatively strongly polar as compared with indene and other substances present in the hydrocarbon oil and which makes the. compound soluble in water or in aqueous solutions of acids or bases, said compound being miscible with the hydrocarbon oil at distillation temperatures, separable therefrom by gravity or on aqueous extraction, chemically inert with respect to the constituents of the hydrocarbon oil, capable of a forming azeotropes with indene and the non-indene oils contained therein, and having a distillation temperature at atmospheric pressure of between about 145 and about 220 0., recovering the hydrocarbon oil 01 high indene content from the still residue, cooling the hydrocarbon oil thus recovered to a'temperature of between about 10 and about -20 0., and separating pure indene from the cooledoil.

11. In a method of producing a hydrocarbon oil of high indene content-from a hydrocarbon oil of relatively low indene content having a boiling range inthe neighborhood of indene boiling point, the step which comprises distilling the hydrocarbon oil of relatively low indene cona tent in the presence of an organic compound having a radical selected from the group consisting of the hydroxyl, the carboxyl, the amino and the pyridinic nitrogen radicals and capable of iorming azeotropes with indene and the non-indene oils contained in the hydrocarbon oil.

12. In a method oil producing a hydrocarbon oil of high indene content, the steps which comprise iractionally distilling a crude selected from the group consisting of coal-tar oils, drip oils, carburetted water-gas tar oils, oil-gas tar oils and light oils recovered in coal-gas and watergas operations to obtain a hydrocarbon mixture of relatively low indene content having a boiling range in the neighborhood of indene boiling point, adding to this hydrocarbon mixture an amount of tar base suflicient to form an azeotrope with non-indene components of the oil, iractionally distilling the mixture, and recovering the hydrocarbon oil of high indene content from the still residue. n

13. In a method of producing a hydrocarbon oil of high indene content, the steps which comprise iractionally distilling a crude selected from the group consisting oi coal-tar oils, drip oils, carburetted water-gas tar oils, oil-gas tar oils and light oils recovered in coal-gas and watergas operations to obtain a hydrocarbon mixture of relatively low indene content having a boiling range in the neighborhood of indene boiling point, adding to this hydrocarbon mixture an amount or mono-ethanol amine sumcient to form an azeotrope with non-indene components or the oil, iractionally distilling the mixture, and recovering the hydrocarbon oil of high indene content from the still residue.

14. In a method of producing a hydrocarbon oil of high indene content, the steps which comprise iractionally distilling a crude selected from the group consi'stinng oi coal-tar oils, drip oils, carburetted water-gas tar oils, oil-gas tar oils and light oils recovered in coal-gas and watergas operations to obtain a hydrocarbon mixture of relatively low indene content having a boiling range in the neighborhood of indene boiling point, adding to this hydrocarbon mixture an amount or ortho-chlorphenol suflicient to form an azeotrope with non-indene components-oi the oil, iractionally distilling the mixture, and recovering the hydrocarbon oil of high indene content, from the still residue.

15. In a method of producing a hydrocarbon oil or high indene content, the steps which comprise i'ractionally distilling a crude selected from the group consisting oi. coal-tar oils, drip oils, carburetted water-gas tar oils, oil-gas tar oils and light oils recovered in coal-gas and watergas operations to obtain a hydrocarbon mixture of relatively low indene content having a boiling range in the neighborhood of indene boiling oint, adding to this hyrocarbon mixture an amount of aniline suflicient to form an azeotrope with non-indene components of the oil, tractionally distilling the mixture, and recovering the hydrocarbon oil oi high indene content from the still residue.

KARL ENGEL. 

